Mikrotron eosens TS3, User Manual, Page: 93 / 120

TS3 User Manual
page 84
Figure 9-3: Focus Chart
Tools required for Back Focus
Adjustment
:
• High quality lens--or lens that
you need to use for a particular
t est --Best if it is very fast--f/1.4
or faster.
• A high quality focus chart can be
very helpful. In a pinch, you can
print one yourself. An 8 1/2 x 11”
or A-Size Seimens Star chart will
work for the example here.
• A 3/32” hex allen wrench for the
C-mount lock screws. (See “TS3
Top View” on page 4 and “TS3
Bo om View” on page 5.)
Appendix E: Adjusting Back Focus
Symptoms of incorrect Back Focus Adjustment:
• Zoom lenses loose focus when zooming in or out. (Not all zoom lenses are designed to remain
focused, so be careful not to prematurely jump to the conclusion that the back focus needs
adjustment.)
• Lenses will not focus at infinit .
• The witness marks (distance marks) on lenses are always off in the same di ection
Adjustment procedure :
1. Connect the TS3 to an LCD display, either via a PC
connection or the HDMI port. Y ou will wish to have
a very good view of the image--the larger the be tt er.
2. Select the lens you wish to use. For our discussion
we will use a 1” format Navitar 50mm f/.95 lens.
3. Decide on a distance. For this discussion we will
use 5’, or 1.5m.
4. Set your target 5’ / 1.5m from the target. The
proper way to measure is from the image plane to
the target. The image plane would be about 17.5 mm
behind the face of the C-mount. Set the target as fl a t
and square to the camera as possible. Usually, taping it
to a wall is the easiest.
5. Get plenty of fl a t white light on the target.
6. Set the TS3 up to frame the image. Using a 50 mm lens at 1.5m, the field of vi e w at 800 x 600
resolution will be ju s t a little la r ger than the focus chart. Use smaller resolutions t o zoom-in
for fine adju s tment.
7. Make a reference mark on the C-mount adapter to mark your starting poi n t. This can be done
with a little dab of whi t e out, or a small piece of tape.
8. Frame and focus the camera on the focus target.
9. Set the lens aperture wide open: f/.95 for this lens.
Figure 9-4: C-Mount